Transcript Geology One: PowerPoint Presentation

From Fossils To Space
Geology #1
What Do We Know?
Solar Nebula Theory
The Solar System
The Primordial Earth
The Primordial Earth
The Solar Nebula Theory
5,000 Ma
4,600 Ma
Fusion
4,500 MaMars-sized impactor
Present
Central disk:
Sun (98.8%)
Hadean Earth
accretion and
differentiation
Hadean Earth
Solid inner & liquid outer core
generate magnetic field
deflect solar wind
Formation of Moon followed
differentiation.
Hadean Earth
Solid inner & liquid outer core
generate magnetic field
deflect solar wind
Formation of Moon followed
differentiation.
Hadean Earth
Composition & Timing
Hadean Earth
Meteorites—leftovers
Ordinary chondrites 4,600 Ma
Carbonaceous chondrites
(5% organics)
Iron (nickel) meteorites
Stony-iron meteorites
Planet density decreases with distance--solar wind
Earth to Sun90,000,000 miles (150 mill Km)
Earth to Moon225,000 miles (380,000 Km)
Earth’s position in the Solar System:
Earth to Sun90,000,000 miles (150 mill Km)
Extremely important:
further awayice
closer insteam
Hadean Atmosphereoutgassing
CO2 (carbon dioxide), H2O (water vapor), CO
(carbon monoxide), H2 (hydrogen gas), HCl
(hydrogen chloride), N2 (nitrogen gas), CH4
(methane), NH3 (ammonia), CH2O
formaldehyde), HCN (cyanide)
Hadean AtmosphereWhat’s missing?
Oxygen generated by:
1. photochemical dissociation
2. photosynthesis
Oxygen RevolutionArchean
Evidence:
1. Banded iron formations ocean sediments
start ~3,000 Ma: end ~1,800 Ma
–UV radiation, purple bacteria, cyanobacteria
Oxygen RevolutionArchean
Evidence:
1. Banded iron formations ocean sediments
start ~3,000 Ma: end ~1,800 Ma
–UV radiation, purple bacteria, cyanobacteria
Oxygen RevolutionProterozoic
Evidence:
1. Banded iron formations
2. Terrestrial red beds red rocks on land
start ~2,300 Ma continues today
Oxygen RevolutionProterozoic
Evidence:
1. Banded iron formations
2. Terrestrial red beds red rocks on land
3. Unstable minerals Uraninite
not present since 2,300 Ma
Oxygen RevolutionProterozoic
Evidence:
1. Banded iron formations
2. Terrestrial red beds red rocks on land
3. Unstable minerals Uraninite
4. Marine copper depositsonly with oxygen
began ~1,700 Ma
Oxygen RevolutionProterozoic
Evidence:
1. Banded iron formations
2. Terrestrial red beds red rocks on land
3. Unstable minerals Uraninite
4. Marine copper depositsonly with oxygen
5. Presence of limestones Proterozoic ocean
(2,000 Ma) carbon dioxide rich
no carbonates
Oxygen RevolutionPhanerozoic
Evidence:
1. Banded iron formations
2. Terrestrial red beds
3. Unstable minerals
4. Marine copper deposits
5. Presence of limestones
Free oxygen leads to ozoneUV protection
Hadean Hydrosphere
Hydrologic cycle:
Water sweated from interior & condensed as rain
Oceans estimated at 4.2 BYA, Australian zircons
Ancient crust
4,000 Ma marks beginning of Archean
Anatomy of a Tectonic Plate
Anatomy of a Tectonic Plate
Formation of Archean Continental Crust
Granulites:
strongly
metamorphosed
and deformed—
tonalite10%
quartz
Strongly
metamorphosed
volcanics and
sedimentary rocks
Formation of Archean Continental Crust
Greenstones:
Strongly
metamorphosed
volcanics and
sedimentary rocks
Granulites:
strongly
metamorphosed
and deformed—
tonalite10%
quartz
Formation of Archean Continental Crust
Greenstones: What does the variation in
composition suggestsubduction zone separation
Formation of Archean Continental Crust
Formation of Archean Continental Crust
Time line
Hadean
4,600 Ma
4,500 Ma
4,400 Ma
4,200 Ma
Solar Nebula, Earth forms
Moon forms
Anoxic atmosphere forms
Oceans start forming
Archean
4,000 Ma Crustal differentiation
3,000 Ma BIF’s, atmospheric oxygen
QUESTIONS?